Reading some other responses, I want to say, gently, that it doesn't really help when someone else says "I had bad tests too but my baby came out fine." Some babies do not come out fine, there is no way of knowing until we actually KNOW which statistic our family will fall into. Reassuring a worrying mother that your baby was born perfectly healthy is akin to telling a woman whose child has just died that it's ok, because it was meant to be. Even if it seems comforting, it simply isn't.
Now, my personal advice as a special needs mom. If your child did end up having special needs, it would be good to know as early as possible. Not because you have to terminate or because it would change the outcome, but it would give you time to grieve the child you lost - the healthy one - and come to terms with being that special needs momma. It is absolutely heartbreaking and life changing when your supposed-to-be-typical child is not typical. I still struggle some days, 18 months after my son was born and suffered a birth injury that left him with cerebral palsy, understanding that it happened and coping with why and how and what-could-I-have-done-differently. My heart still breaks to think about the difficult future he can have, the difficult present he is going through, and I don't think that heartbreak will ever stop. I found out too late that there were measures that could have been done at birth to lower his chances of disability. It hurts, as his momma I want to do everything in the world to help him and make his life easier, and if I had had the time to prepare prior to his birth, I could have been way ahead of the game, so to speak.
I would encourage you to get further testing done to know for certain. Amnios truly do have a very low risk - I had one, it wasn't painful and nothing bad came of it. If the answer is negative, you can put this stressful worrisome burden out of your mind for the rest of your life and enjoy your typical pregnancy. If the answer is positive, you can grieve (as you will need to, I promise you) and educate yourself on how to be the BEST mother you can be to your baby, get insurance referrals and therapy lined up for whatever special care he will require, and you can start to move past those difficult things, so that when your baby is born you can enjoy every moment and know that you did every thing you could to ready yourself to be the best mom possible.
Whatever you do decide, I wish you encouragement and strength and a strong heart. Joining the ranks of special needs mothers introduces you to a very exclusive club that lasts a lifetime and will give you rewards you've never even dreamed of.... hugs to you.